Polyolefins such as high density polyethylene (HDPE) homopolymer and linear low density polyethylene (LLDPE) copolymer can be produced using various combinations of catalyst systems and polymerization processes. Medium or high density polymers with a high molecular weight and a broad molecular weight distribution often have a combination of relatively easy processing, superior melt strength, and a good balance of stiffness and physical properties. In some end-use applications, however, it can be beneficial to have this combination of properties, but also to have improved puncture, impact, and tear resistance. Accordingly, it is to these ends that the present invention is directed.